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2D games and antialiasing

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Now that N/A is in use, I stumbled to one simple problem: does antialiasing apply to games that are 2D? We already know FOV and anisotropic filtering doesn't.

For most part 2D games are done in way that sprites themselves are antialiased or done in pixel style. However some games like Metal Slug 3 and emulators like zsnes allows you to apply filters which smooths out upscaled pixel graphics (2xSAI, HQ filter, Super Eagle) that are used more with image scaling than antialiasing. They also include other filters like scanlines and CRT effect. Even Desmume only includes filters as they can't increase internal 3D resolution yet.

I would say 2D games should be N/A for antialiasing as they don't use regular 3D antialiasing methods. Other way of doing things is to make it true/false and then list what upscaling and filtering methods game uses as filters technically remove aliasing.

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This might sound weird and off-topic, but... I've just now realized, that if you make a line in Paint, that isn't entirely vertical or horizontal, it's going to be - by default - extremely jaggy. But if I were to make such line in Photoshop - I'll get an option to make it smooth... and now, I've finally realized - that yes, there is a point in Anti-aliasing in 2D graphics. Not like, it's extremely crucial to have it, as many 2D games already have a fixed camera position and they will not apply any rotation to it, not to mantion many of the sprites used in such games are already smoothed out, but I guess distinguishing whatever AA should be n/a or false is a waste of time and we won't be hurting old games, if we just state it's false.

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I might be mistaken, but purely 2D games can and sometimes feature anti-aliasing settings. Its purpose is essentially to get rid of jagged edges. It can be applied to any geometrical shape, and is used in sprite based games 2D (as in flat, not 3D graphics, models, nothing of the kind).

Can you give me example as I said in first post that usually that antialiasing is image filter which gets rid of pixelated sprites instead of aliasing.

This might sound weird and off-topic, but... I've just now realized, that if you make a line in Paint, that isn't entirely vertical or horizontal, it's going to be - by default - extremely jaggy. But if I were to make such line in Photoshop - I'll get an option to make it smooth... and now, I've finally realized - that yes, there is a point in Anti-aliasing in 2D graphics. Not like, it's extremely crucial to have it, as many 2D games already have a fixed camera position and they will not apply any rotation to it, not to mantion many of the sprites used in such games are already smoothed out, but I guess distinguishing whatever AA should be n/a or false is a waste of time and we won't be hurting old games, if we just state it's false.

You must be using really old paint. Windows 7 zoom 800% from bottom right and draw line slowly and it applies AA to it. With photoshop/gimp you can draw lines also without antialiasing if needed though.

To me it just seems slightly unfair for 2D games in general to make AA false as even if they did introduse AA for them sprites on older titles are pretty small so AA just makes them blurry. For newer games like Dust: an Elysian Tail you can't see single aliased edge anywhere and that game has literally every PC option it can have so AA is clearly N/A for that.

If I'm not totally incorrect then game basically renders vector model which causes aliasing in that particular title and antialiasing is definitly needed. Flash games like Binding of Isaac also features vectors and flashs presets high, medium and low are basically AA levels. BUT we also have games like Machinarium which use flash but also use sprites...

Spoilers next:

Then we have titles like FEZ which basically is 2D pixel art game done with 3D engine so by default FOV and AA are not needed but after beating game once you get first person view where they should be present.

I agree with Garrett that if game is purely 2D games using sprites (like Dust or Metal Slug 3) then FOV, AF and AA should be N/A.

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Here's what happens to that bunch of pixels, when you apply rotation (on only axis available in 2D space).

And when you smooth it out:

It's a rare example, yes. But I'm guessing, if you'd have a 2D platformer (based on sprites), where a ground is entirely flat. And then you'd turn a camera just a bit - you'd see exactly that. And so started thinking, was there a 2D platformer, where that would be the case.... yes, there was:

Found on YouTube (hence a bit of upscaling) - the game is "I wanna be the boshy".

Indeed it's pointless to apply anti-aliasing to most old games, which were designed with a fixed camera perspective and already had "anti-aliasing" in spire alpha channels. But I just wanted to give an example, that yes - antialiasing applies also to 2D game, even if its graphics are not based on vectors.

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For the field of view.. I'm not sure though.. because actually if you could "zoom" in and or out the 2D area displayed, the core principle would be similar to that in 3D games..

Not exactly, since it's a scaling of 2D objects/2D plane, not actually increasing the field of view which is a function that applies to a 3D camera (and as such is usually only needed in FPP and TPP games... with some exceptions for RTS games that have ridiculous "zoom"). Yes, we could state whatever the game has some scaling, but a lot of the games will have scaling based on the rendering resolution, anyway (the higher the resolution - the smaller the objects).

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Not exactly, since it's a scaling of 2D objects/2D plane, not actually increasing the field of view which is a function that applies to a 3D camera (and as such is usually only needed in FPP and TPP games... with some exceptions for RTS games that have ridiculous "zoom"). Yes, we could state whatever the game has some scaling, but a lot of the games will have scaling based on the rendering resolution, anyway (the higher the resolution - the smaller the objects).

I remember playing sims always with 800x600 as it had better zoom and larger icons. CRT and inaccurate ball mouse times :)

Well that was really good example. That actually made me think that I have played Dust 100% trough and I know it has lots of rotating sprites everywhere and not single aliased edge is visible ever. Could it be that some games has mandatory antialiasing applied as rotated sprites would look absolutely awful?